Astronomers in France, Germany, and the U.S. traced the origin of Theia using ancient lunar and terrestrial rocks.
Theia, the planet that collided with early Earth, likely formed closer to the Sun than previously thought.
For decades, scientists believed Theia struck Earth about 4.5 billion years ago, scattering debris that formed the Moon.
The giant impact theory has guided research since the first Apollo samples over 50 years ago.
Theia vanished billions of years ago, leaving no direct chemical evidence, so researchers had to find indirect clues.
Jake Foster of the Royal Observatory Greenwich said the study almost precisely pinpoints Theia’s birthplace.
He emphasized that scientists can now trace a planet that disappeared 4.5 billion years ago.
Reverse Engineering Planetary Origins
The team analysed isotopes in Earth rocks and Apollo lunar samples to act as chemical fingerprints.
Earth and Moon rocks share nearly identical metal isotope ratios, complicating identification of Theia’s material.
Researchers tested isotopes of iron, chromium, zirconium, and molybdenum to reconstruct early-Earth and Theia scenarios.
They modelled hundreds of combinations to see which matched today’s isotopic signatures.
Isotopes vary depending on formation distance from the Sun, revealing clues about planetary origins.
By comparing these patterns, scientists concluded Theia formed in the inner Solar System, closer to the Sun than Earth.
Previous studies had suggested Theia formed farther from the Sun, but new data challenges that view.
Unlocking Early Solar System Mysteries
The study offers new insight into how planets grow, collide, and evolve in early Solar System stages.
Researchers hope their methods will guide future studies of planetary formation and interactions.
Tracing Theia helps scientists understand the chemical and physical processes that shaped Earth and Moon.
The work highlights the value of isotopic analysis in reconstructing vanished planets.
Scientists plan to expand this approach to study other early Solar System bodies.
By learning where planets like Theia originated, researchers can refine models of planetary evolution.
This research strengthens understanding of collisions, debris formation, and early Solar System dynamics.
